In recent years, in mobile electronic devices such as mobile telephones and personal data assistants, numerous functions such as voice, transmission and reception of e-mail, Internet access, and games are demanded. These mobile electronic devices are provided with for example a sliding structure.
FIG. 6 is a schematic sectional configuration diagram that shows an example of a common mobile electronic device that has a sliding structure. A mobile electronic device 100 that is shown in FIG. 6 has a first case 101 that is provided with a display device such as a liquid crystal and a second case 102 that is provided with an input device such as a keyboard or numeric keypad. In the mobile electronic device 100, the first case 101 and the second case 102 face each other in the state of having a predetermined gap G, and so sliding is possible. The cases 101, 102 include circuit boards 103, 104, respectively. The circuit boards 103, 104 are electrically connected by a flexible flat cable 105. The flexible flat cable 105 is provided so as to slide while making contact with facing surfaces 106, 107 of the cases 101, 102. The flexible flat cable 105 is installed in a state of being bent in a U-shape in the gap G between the cases 101, 102. The flexible flat cable 105 follows the sliding operation of the cases 101, 102, and is provided so that a U-shaped bend portion 108 is displaced in the direction X in which the cases 101, 102 slide (called the sliding direction, and hereinbelow referred to as such). The facing surfaces 106, 107 with which the flexible flat cable 105 makes contact are also called “sliding surfaces.”
At this time, the flexible flat cable 105 is fixed to the cases 101, 102 with securing end portions 109. The flexible flat cable 105 is installed in the state of making contact with the facing surfaces 106, 107 (sliding surfaces) at regions from the securing end portions 109 to the maximum diameter portions 110 of the U-shaped bend portion 108. The circuit boards 103 and 104 have connectors 111, 112, respectively. The flexible flat cable 105 is connected to those connectors 111, 112.
In the electronic device 100 that has this kind of sliding structure, due to the cases 101, 102 repeatedly performing a sliding operation, the flexible flat cable 105 repeatedly comes into contact with the facing surfaces 106, 107 (sliding surfaces). Deformation such as kinking and the like occurs in the flexible flat cable 105 due to friction that is produced during contact with the facing surfaces 106, 107, and as a result, the problem arises of the flexible flat cable 105 breaking. FIG. 7A and FIG. 7B are descriptive views of the breakage configuration of the flexible flat cable in the case of having caused the mobile electronic device shown in FIG. 6 to undergo a repeated sliding operation. FIG. 7A and FIG. 7B are schematic sectional views that show the configuration of a flexible flat cable before and after a sliding operation. In a mobile electronic device that has a conventional sliding structure, by repeating the sliding operation, the flexible flat cable 105 repeatedly makes contact with the facing surfaces 106, 107 in the region from the securing end portions 109 to the maximum diameter portions 110 of the U-shaped bend portion 108. Deformation such as kinking and the like occurs in the flexible flat cable 105 due to friction that is produced during contact with the facing surfaces 106, 107, and as shown in FIG. 7A and FIG. 7B, there has been the problem of line breakage caused by that kinking easily occurring.
Patent Document 1 below proposes a slide-type electronic device for preventing breakage of the flexible lead sheet. In a first case of the slide-type electronic device, a first guide surface extending in parallel with a circuit board is provided at a position of the same height as a terminal portion of the flexible lead sheet that is connected to a connector. Also, in a second case that faces the first case, a second guide surface extending in parallel with the first guide surface is provided at a position of the same height as a terminal portion of the flexible lead sheet that is connected to a connector. In this slide-type electronic device, by providing the first guide surface and the second guide surface, when the flexible lead sheet undergoes bending deformation along both guide surfaces, the curvature radius of the U-shaped bend portion is maintained constant and it is possible to avoid the U-shaped bend portion receiving an impact, and as a result, it is possible to prevent line breakage.
However, even in the slide-type electronic device that was proposed in Patent Document 1 above, there is the risk of deformation such as kinking and the like and line breakage easily occurring due to friction that occurs when the flexible sheet lead makes repeated contact with the first guide surface and the second guide surface, in the same manner as the case described in FIG. 6, FIG. 7A and FIG. 7B.
Although Patent Documents 2 and 3 below do not disclose art related to mobile electronic devices, they do disclose related art related to installation modes of flexible printed circuit wiring boards that have U-shaped bend portions. Patent Document 2 proposes art to prevent a flexible printed circuit wiring board from being damaged by contact with a tray bottom face. In this art, at the connection end portion of a flexible printed circuit board that is arranged so as to be bent in U-shape, an extension portion that extends from the connection end portion is provided. The extension portion limits deformation of the flexible printed circuit board to the tray side, and so it is possible to avoid the flexible printed circuit board making contact with the tray bottom face. Also, paragraph 0046 of Patent Document 3 given below discloses that due to one end of a flexible flat cable being held by a carriage, reactive force due to bending of the flexible flat cable by that carriage is exerted.